Texmaker 5 forward/backward search

I think that the "forward Backward" search is something of the "Find" (cntrl-F) possibility (image from Windows 7):

I would guess by now you have resolved this since your right to say by default it should be working!

When a TeX editor compiles a PDF file using the compiler "-synctex=1" option , then from that PDF if / when you see an issue, you can right click to trigger & select jump back to editor, such as to find that location in the TeX. Also you can equally jump forward from the editor to preview the same location in the PDF. Note each compile PDF command may need this option, there is a different command for syncing with DVI output.

Some users have found (depending on related system issues) that synctex is "out of sync" or worse "not working with some files", this may be due to

Bad command (synctex missing is rare), Check placement of -synctex=1
Out of date / mismatched synctex components
Corruption of sync file (avoid sync drives such as dropbox or cloud drives)
Avoid file or path names with blank spaces (sporadically work)
Avoid UTF characters in file or path names (sporadically work)
Avoid punctuation -._= characters in file or path names (sporadically work)

If not take a look at my answer to Wrong placement of Cursor Position there the answer was a rogue .synctex.gz however if you follow the links therein you will find other common reasons for synctex to not be working such as "path names" and Àccented characters